Etchant rinse apparatus

ABSTRACT

Residual etchant, such as acid and the like remaining on articles such as printed circuit boards that have been etched, contains a metallic chemical component, such as copper. When this residual etchant is rinsed from the articles (such as printed circuit boards), it contaminates the water of the rinse. The chemical replacement of copper ions in the rinse with aluminum ions by passing the rinse through a basket filled with aluminum turnings, and recycling the rinse thus passed back for reuse at the rinsing station continuously renders the rinsing water free of copper, to permit periodic discharge of the rinse water to sewage or the like.

United States Patent Goffredo et al.

ETCHANT RINSE APPARATUS Inventors: Daniel L. Goffredo, Riverton, N..I.;

John Alfred Dunkelberger, Jr., Centre Hall, Pa.

Chemcut Corporation, State College, Pa.

Filed: Oct. 18, 1971 Appl. 180.: 190,136

Assignee:

1m. 0. B08b 3/02, B08b 3/10 Field 01 Search ..134/109,111,131,151,134/199, 83, 10-, 150/345; 210/287, 433

References Cited UNITED STATES PATENTS 4/1948 Zademach et a1. 134/111 X3/1963 Benton et a1, 134/151 X 6/1966 Reid et a]. .1 134/10 X 1451 Mar.18, 1 975 3,431,921 3/1969 Pesek 134/131 X 3,603,329 9/1971 White eta1.. 134/199 X 3,705,061 12/1972 King 134/10 X Primary E.\'aminer-RobertL. Bleutge Attorney, Agent, or FirmPaul & Paul [57] ABSTRACT Residualetchant, such as acid and the like remaining on articles such as printedcircuit boards that have 'been etched, contains a metallic chemicalcomponent,

such as copper. When this residual etchant is rinsed from the articles(such as printed circuit boards), it contaminates the water of therinse. The chemical replacement of copper ions in the rinse withaluminum ions by passing the rinse through a basket filled with aluminumturnings, and recycling the rinse thus passed back for reuse at therinsing station continuously renders the rinsing water free of copper,to permit periodic discharge of the rinse water to sewage or the like.

6 Claims, 2 Drawing Figures PATENTEU MAR] 81975 sumlurg- ETCHANT RINSEAPPARATUS BACKGROUND OF THE INVENTION In the art of etching printedcircuit boards and the like, it has been commonplace to rinse acidetchants from the printed circuit boards, for purposes of cleaning" theacid from the boards, in order that the boards may be subsequentlyhandled by personnel, and also to assure the termination of the etchingprocess, on copper components of the board. Such washing or rinsing hasconventionally been done by spraying the boards with a water rinse, andeither continuously or periodically replacing the water rinse, with usedwater rinse being discharged to sewage or the like. However, such usedwater rinse in accordance with the abovementioned prior art techniqueshas contained copper ions therein, and such has been found to causeundesirable ecological effects upon streams, waterways and the like.into which the used rinse eventually finds its way from sewage.

Furthermore, the copper contained within the acid rinsed off the boardsin accordance with these prior art techniques has been permanently lost.

SUMMARY OF THE INVENTION The present invention is directed towardproviding an apparatus whereby recycling of the rinse water is possiblewithout building up an undesirable level of copper concentration in therinse water, and whereby the rinse water is not contaminated by copper,so that the same may be discharged into conventional sewage lines,streams, etc., without producing damaging environmental effects. Aportion of the rinse water being delivered to spray nozzles passes fromthe reservoir of rinse water to and through a particulate material(preferably aluminum turnings), and the rinse water is dispersedtherethrough, eventually being returned to the rinse reservoir. Duringits passage through the aluminum turnings, a chemical replacement ofcopper ions in the rinse is effected, by replacement with aluminum ions,with the copper ions being reduced to metallic copper, and with thealuminum being oxidized and flowing into solution in the rinse water.The rinse water thus accumulates an aluminum ion concentration, whichmay periodically be discharged as desired, without producing undesirableenvironmental effects.

Accordingly, it is a primary object of this invention to provide a novelapparatus for treating etchant rinse water.

It is a further object of this invention to provide a novel apparatusfor replacing copper ions in etchant rinse water with aluminum ions.

It is another object of this invention to provide a novel apparatus forrinsing etchant reactants from articles that have been etched, whereinsuch apparatus involves chemical replacement of unwanted metallic ionsin the rinse medium.

Other objects and advantages of the present invention will be readilyapparent to those skilled in the art from a reading of the followingbrief descriptions of the drawing figures, detailed description of thepreferred embodiment, and the appended claims.

IN THE DRAWINGS FIG. 1 is a transverse sectional view through theseveral components of a rinsing apparatus of this invention.

like.

FIG. 2 is .a longitudinal sectional view through a portion of therinsing apparatus illustrated in FIG. 1, and illustrating the manner inwhich the rinse is sprayed onto printed circuit boards or the likepassing through a rinse chamber from an etching chamber or the like.

Referring to the drawings in detail, reference is first made to FIG. 2,wherein an upstream chamber 10 is illustrated, as comprising an etchingchamber, or if desired, a chamber for first physically removing etchantfrom printed circuit boards 11 or the like conveyed therethrough, bymeans other than water spraying. The printed circuit board 11 for whichthis apparatus has been developed, is then delivered into a rinsingchamber 12, passing along a plurality of driven rollers 13, which rotatein a clockwise direction as viewed in the illustration of FIG. 2, formovement of the printed circuit board 11 in the direction of the arrow14 of FIG. 2, through the chamber 12 for eventual discharge through theoutlet 19, thereof, to a drying station or the The board 11, upon itsdelivery to the chamber 12 may have residual components of an etchingacid, such as ferric chloride thereon, that has been used to etchunmasked copper portions of the printed circuit boards, and suchresidual etchant thus contains a certain copper content.

The board 11 then passes between upper and lower sets of spray nozzles15 and 16, that are supplied with water under pressure, for spraying theboard 11 through a certain zone such as that indicated in FIG. 2, withthe zones of spray of the nozzles combining transversely of the machine,in order to completely spray a board 11 carried therebetween as will bemore clearly apparent with reference to the illustration of FIG. 1. Theupper spray nozzles 15 are connected to rinse water header 17, and thelower spray nozzles 16 are each connected to a lower rinse water header18, with the headers 17 and 18 being supplied with rinse water from acommon delivery line 20. After spraying of the board 11 with rinse waterpassing through the nozzles 15 and 16, the rinse water 21 drops into areservoir 22, and such rinse water 21 and the reservoir 22 now has aslight concentration of copper ions therein. Rinse water 21 is deliveredfrom a chamber 22, by a pump 23, or other suitable device, whichreceives the rinse water 21 at a lower inlet 24 thereof, and deliversthe same through an outlet line 25, with the pump 23 being driven by anelectrical motor 26 or the like disposed outwardly of the chamber 22,but connected to the pump 23 through a rotatable shaft 27 that passesinto the chamber 22 from outside thereof, to drive the submerged pump23.

Rinse water is thus delivered through the line 25, outwardly of thechamber 22, with the delivery line 25 being bifurcated at the piping tee29, with some of the rinse water being delivered to the spray nozzles 15and 16, through the line 20, and some of the rinse water being deliveredthrough a replacement chamber 28, and back into the reservoir 22 througha return line 30, selectively openable upon actuation of a switch 31 orthe like, as desired, whereby rinse water is delivered to thereplacement chamber 28, as a parallel loop to that delivered to thespray nozzles 15 and 16. Thus, rinse water enters the replacementchamber 28, being delivered thereto by a suitable piping line 32, andpassing through a generally open shut-off switch 33, entering thereplacement chamber28, through the bottom 34 thereof, at a centralopening thereof, for passage outwardly of a plurality of holes 35, orother suitable perforations in the outer surface of a hollow cylindricalupstanding standpipe 36, as illustrated in FIG. 1.

A removable tank 37 is provided, inwardly of the replacement chamber 28,the bottom of which has a blind hole therein for facilitating thedisposition of the tank 37 over the standpipe 36, and with the sides ofthe blind hole 38 in the tank 37 facilitating the passage inwardly ofrinse water'into the interior 40 of the tank, as such rinse water passesthrough perforations 35 of the standpipe 36. The tank 37 is constructedas a basket, with the outer cylindrical surface 41 thereof also beingperforate, and with the basket being filled with a particulate materialsuch as aluminum turnings whereby the rinse water 21 delivered throughthe line 32 will pass through the aluminum turnings, to be dischargedthrough the tank 37, but passing through perforations in the outer wall41 is spaced inwardly of the inner surface of the chamber 28, to form anannular void therein, for passage of water upwardly, inasmuch as thewater is under pressure from the pump 23, and with the water thus beingredelivered through the line 30 as aforesaid, into the chamber 22.

The tank 37 is also provided with a handle 43 whereby the same mayreadily be grasped and removed from its position over the standpipe 36,upon opening the lid 44 of the chamber 28, whenever the concentration ofcopper within the aluminum turnings necessitates replacement of the tank37, or of the turnings carried therein.

It will be apparent from all of the foregoing, that during the passageof the rinse water through the aluminum turnings within the tank 37, thedissolved copper content within the rinse is chemically replaced withaluminum from the aluminum turnings, and the copper ions removed fromthe rinse are reduced to metallic copper and aluminum is oxidized, goinginto solution in the rinse water. The water reservoir thus remainsextremely low in copper ion concentration, but will progressivelyincrease in aluminum ion concentration. Upon the reservoir 22 achievingan objectionable level of aluminum ion concentration, the rinse water 21therein may be discharged to sewage or the like, without causingcontamination of sewage lines, waterways, or the like.

The herein discussed invention is significant in that it provides asimple and low cost means of eliminating objectionable copper ions frometchant rinse water. Accordingly, a highly desirable anti-pollutionfeature is encompassed by the present invention, which replaces copperion concentration in rinse water with more acceptable aluminum ions.

While displacement reactions themselves are previously known, forremoving copper from solution generally, and wherein such processes aregenerally known as cementation, in the mining industry, for example, theuse of replacement ions to resolve a heretofore difficult pollutionproblem for the etching industry, and particularly for the industryrelating to the etching of printed circuit boards is highly desirable.

It will also be apparent that other types of chemical replacement may beeffected, in lieu of using aluminum particles within the tank 37. forexample, iron filings, magnesium, or any other metal above copper in theelectromotive series, or any other substance that will effect thedesired ion exchange, preferably with regard to its adaptability toachieving the other desired ends of this invention as set forth herein,may be utilized within the tank 37, if desired, for replacement ofcopper ions with iron ions in the solution.

Another feature of this invention is that the process permits continuousreplacement of copper ions in the rinse water, by permitting continuousremoval, by displacement reactions onto the aluminum surfaces of theparticles within the tank 37. It will, however, be apparent that theparallel loop arrangement illustrated in FIG. 1 is not to be construedas limiting, in that rinse water 21 from the tank 22 may pass seriallyfirst to the tank 37, and then to the spray nozzles 15 and 16, ifdesired, or the converse.

It will be apparent from the foregoing that various modifications may bemade in the details of construction of the apparatus of this invention,as well as in the method of use thereof, all within the spirit and scopeof theappended claims.

What is claimed is:

l. A rinsing appartus for rinsing etching reactant from articles thathave been etched by a reactant comprising a rinsing chamber, means forconveying etched articles through the chamber, rinse dispensing memberslocated in said chamber and positioned for dispensing rinsing liquidonto the articles in the chamber, a rinse reservoir for containing arinsing liquid, means for delivering rinsing liquid from said reservoirto said dispensing members, a replacement chamber having an inletconnected for receiving rinse liquid from said reservoir and having anoutlet connected for recycling the rinse liquid for delivery to thereservoir, said replacement chamber including a tank containing adisplacing material and means for facilitating flow of rinse liquid fromthe inlet through the displacing material in the tank and to the outlet,with the displacing material comprising means facilitating an ionreplacement of etchant ions in the rinse liquid with ions from thedisplacing material, wherein said means for delivering rinsing liquidincludes pump means for delivery of liquid simultaneously to both therinse dispensing members and the replacement chamber.

2. The apparatus of claim 1, wherein said displacing material isparticulate material.

3. The apparatus of claim 2, wherein the articles being etched containcopper with the rinse containing a substantial concentration of copperions, and wherein said particulate material comprises aluminum particlesfor chemical replacement of copper ions with aluminum ions.

4. The apparatus of claim 3, wherein said pump means includes a pump,having a discharge therefrom bifurcated for delivery both to the rinsingmembers and to the replacement chamber, wherein said tank is disposedwithin said replacement chamber centrally thereof, and spaced from thewalls of the chamber thereof, and with said flow facilitating meansincluding a central inlet of rinse liquid to the tank, and with tankwalls being perforate for discharge of liquid therethrough to the outletof said replacement chamber, wherein said dispensing members comprisespray nozzles, and wherein said conveying means comprises means formoving the articles along a generally horizontal path, with said spraynozzles being disposed both above and below the path for spraying upperand lower sides of articles conveyed therealong.

thereof, and with said flow facilitating means including a central inletof rinse liquid to the tank, and with the tank walls being perforate fordischarge of liquid therethrough to the outlet of said replacementchamber.

1. A RINSING APPARTUS FOR RINSING ETCHING REACTANT FROM ARTICLES THATHAVE BEEN ETCHED BY A REACTANT COMPRISING A RINSING CHAMBER, MEANS FORCONVEYING ETCHED ARTICLES THROUGH THE CHAMBER, RINSE DISPENSING MEMBERSLOCATED IN SAID CHAMBER AND POSITIONED FOR DISPENSING RINSING LIQUIDONTO THE ARTICLES IN THE CHAMBER, A RINSE RESERVOIR FOR CONTAINING ARINSING LIQUID, MEANS FOR DELIVERING RINSING LIQUID FROM SAID RESERVOIRTO SAID DISPENSING MEMBERS, A REPLACEMENT CHAMBER HAVING AN INLETCONNECTED FOR RECEIVING RINSE LIQUID FROM SAID RESERVIOR AND HAVING ANOUTLET CONNECTED FOR RECYCLING THE RINSE LIQUID FOR DELIVERY TO THERESERVOIR, SAID REPLACEMENT CHAMBER INCLUDING A TANK CONTAINING ADISPLACING MATERIAL AND MEANS FOR FACILITATING FLOW OF RINSE LIQUID FROMTHE INLET THROUGH THE DISPLACING MATERIAL IN THE TANK AND TO THE OUTLET,WITH THE DISPLACING MATERIAL COMPRISING MEANS FACILITATING AN IONREPLACEMENT OF ETCHANT IONS IN THE RINSE LIQUID WITH IONS FROM THEDISPLACEING MATERIAL, WHEREIN SAID MEANS FOR DELIVERING RINSING LIQUIDINCLUDES PUMP MEANS FOR DELIVERY OF LIQUID SIMULTANEOUSLY TO BOTH THERINSE DISPENSING MEMBERS AND THE REPLACEMENT CHAMBER.
 2. The apparatusof claim 1, wherein said displacing material is particulate material. 3.The apparatus of claim 2, wherein the articles being etched containcopper with the rinse containing a substantial concentration of copperions, and wherein said particulate material comprises aluminum particlesfor chemical replacement of copper ions with aluminum ions.
 4. Theapparatus of claim 3, wherein said pump means includes a pump, having adischarge therefrom bifurcated for delivery both to the rinsing membersand to the replacement chamber, wherein said tank is disposed withinsaid replacement chamber centrally thereof, and spaced from the walls ofthe chamber thereof, and with said flow facilitating means including acentral inlet of rinse liquid to the tank, and with tank walls beingperforate for discharge of liquid therethrough to the outlet of saidreplacement chamber, wherein said dispensing members comprise spraynozzles, and wherein said conveying means comprises means for moving thearticles along a generally horizontal path, with said spray nozzlesbeing disposed both above and below the path for spraying upper andlower sides of articles conveyed therealong.
 5. The aparatus of claim 1,wherein said dispensing members comprise spray nozzles.
 6. The apparatusof claim 1, wherein said tank is disposed within said replacementchamber centrally thereof, and spaced from the walls of the chamberthereof, and with said flow facilitating means including a central inletof rinse liquid to the tank, and with the tank walls being perforate fordischarge of liquid therethrough to the outlet of said replacementchamber.